[Clas12_rgb] [EXTERNAL] RGB summary for Jan 9, 2020

[Gilfoyle, Jerry]

Summary of last day (or so) (1/9/20)


Started production running at 50 nA, but saw large fluctuations in livetime, rise in DC 
occupancies, and very high rate of signals from mvt1 and mvt2. Tried lower beam current. Began
investigation of livetime, trigger timing, etc.

DC occupancies - Monitoring hists show Region 1 average occupancy of 6%. Not clear
     	       	 yet what is the cause of this. Did not see it in December. Under investigation.
     	       - Other systems show occupancies that are within a few percent of 
	       	 past performance (Dec 2019, spring 2019)
	       - getting gas mixture back to previous conditions. will take a while
	       	 because of large buffer volumes.

trigger-timing - large amplitude oscillations in the trigger-time distribution between
	       	 successive events. 
	       - Seen before in HPS. Related to 100 kHz noise in the injector.
	       - large variations and low values of livetime.
	       - tuned the Hall B laser phase angle in the injector (expert called in).
	       - oscillations disappeared, but returned. see entry 3760346.
	       	 https://logbooks.jlab.org/entry/3760346
	       - owl shift mapped out the peak-to-valley ratio vs. laser phase angle and
	         lowered the beam current.
	       - oscillations disappeared again, live time good. will see if it lasts.
	       
Response to items above.
	- start analysis to study to study both problems in low-luminosity data (10 nA)
	  and compare with high-luminosity runs (40, 50 nA) taken this week.
	- work being done to improve gas mixture.
	- Accel. working on injector noise.

New hole in DC occupancy plot - appears to be related to electronics (not the chamber
    	 wires), was failed DCRB board.

Bluejeans - New address for RC meetings: bluejeans.com/8928008153.

Upcoming
     Hall C: Will have a new Wien angle at the injector (and thus our 
     	     polarization will change) when they start
	     They have been delayed by target polarization problems which appear to
	     be solved (or getting there).



-----
Dr. Gerard P. Gilfoyle
Physics Department
University of Richmond, VA 23173  USA
e-mail: ggilfoyl at richmond.edu
phone:  804-289-8255